Semi-mobile group (3)
I believe the answer is:
mob
'group' is the definition.
The answer is an example.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mob that I've seen before include "Kind of cap" , "An undisciplined gang of people" , "Crime syndicate or disorderly crowd" , "Rowdy crowd" , "Unruly crowd" .)